Highly transparent Er:YAG ceramics were fabricated by solid-state reactive sintering using a mixture of commercial a-Al2O3, Y2O3, and Er2O3 powders with tetraethoxysilane and MgO as sintering aids. A fully dense 1.0 at.% Er:YAG ceramic with an average grain size of similar to 25 mu m was obtained by vacuum sintering at 1800 degrees C for 30 h. The in-line transmittance reached 83% near the lasing wavelength of 1645 nm with a scattering loss of similar to 0.02 cm-1. Laser operation of such a Er:YAG ceramic rod (4.0 mm x 4.0 mm x 10.8 mm) was demonstrated at 1645 nm with a slope efficiency of 51% under resonant pumping at 1532 nm, and the maximum continuous-wave laser output was 13 W.